Life beyond our universe: Physicists explore the possibility of life in universes with laws different from our own

Feb 22, 2010 by Anne Trafton

(PhysOrg.com) -- Whether life exists elsewhere in our universe is a longstanding mystery. But for some scientists, there?s another interesting question: could there be life in a universe significantly different from our own?

A definitive answer is impossible, since we have no way of directly studying other universes. But cosmologists speculate that a multitude of other universes exist, each with its own laws of physics. Recently physicists at MIT have shown that in theory, alternate universes could be quite congenial to life, even if their physical laws are very different from our own.

In work recently featured in a cover story in Scientific American, MIT physics professor Robert Jaffe, former MIT postdoc, Alejandro Jenkins, and recent MIT graduate Itamar Kimchi showed that universes quite different from ours still have elements similar to carbon, hydrogen, and oxygen, and could therefore evolve life forms quite similar to us. Even when the masses of the elementary particles are dramatically altered, life may find a way.

“You could change them by significant amounts without eliminating the possibility of organic chemistry in the universe,” says Jenkins.

Pocket universes

Modern cosmology theory holds that our universe may be just one in a vast collection of universes known as the multiverse. MIT physicist Alan Guth has suggested that new universes (known as “pocket universes”) are constantly being created, but they cannot be seen from our universe.

In this view, “nature gets a lot of tries — the universe is an experiment that’s repeated over and over again, each time with slightly different physical laws, or even vastly different physical laws,” says Jaffe.

Some of these universes would collapse instants after forming; in others, the forces between particles would be so weak they could not give rise to atoms or molecules. However, if conditions were suitable, matter would coalesce into galaxies and planets, and if the right elements were present in those worlds, intelligent life could evolve.

Some physicists have theorized that only universes in which the laws of physics are “just so” could support life, and that if things were even a little bit different from our world, intelligent life would be impossible. In that case, our physical laws might be explained “anthropically,” meaning that they are as they are because if they were otherwise, no one would be around to notice them.

Jaffe and his collaborators felt that this proposed anthropic explanation should be subjected to more careful scrutiny, and decided to explore whether universes with different physical laws could support life.

This is a daunting question to answer in general, so as a start they decided to specialize to universes with nuclear and electromagnetic forces similar enough to ours that atoms exist. Although bizarre life forms might exist in universes different from ours, Jaffe and his collaborators decided to focus on life based on carbon chemistry. They defined as “congenial to life” those universes in which stable forms of hydrogen, carbon and oxygen would exist.

“If you don’t have a stable entity with the chemistry of hydrogen, you’re not going to have hydrocarbons, or complex carbohydrates, and you’re not going to have life,” says Jaffe. “The same goes for carbon and oxygen. Beyond those three we felt the rest is detail."

They set out to see what might happen to those elements if they altered the masses of elementary particles called quarks. There are six types of quarks, which are the building blocks of protons, neutrons and electrons. The MIT team focused on “up”, “down” and “strange” quarks, the most common and lightest quarks, which join together to form protons and neutrons and closely related particles called “hyperons.”

In our universe, the down quark is about twice as heavy as the up quark, resulting in neutrons that are 0.1 percent heavier than protons. Jaffe and his colleagues modeled one family of universes in which the down quark was lighter than the up quark, and protons were up to a percent heavier than neutrons. In this scenario, hydrogen would no longer be stable, but its slightly heavier isotopes deuterium or tritium could be. An isotope of carbon known as carbon-14 would also be stable, as would a form of oxygen, so the organic reactions necessary for life would be possible.

The team found a few other congenial universes, including a family where the up and strange quarks have roughly the same mass (in our universe, strange quarks are much heavier and can only be produced in high-energy collisions), while the down quark would be much lighter. In such a universe, atomic nuclei would be made of neutrons and a hyperon called the “sigma minus,” which would replace protons. They published their findings in the journal Physical Review D last year.

Fundamental forces

Jaffe and his collaborators focused on quarks because they know enough about quark interactions to predict what will happen when their masses change. However, “any attempt to address the problem in a broader context is going to be very difficult,” says Jaffe, because physicists are limited in their ability to predict the consequences of changing most other physical laws and constants.

A group of researchers at Lawrence Berkeley National Laboratory has done related studies examining whether congenial universes could arise even while lacking one of the four fundamental forces of our universe — the weak nuclear force, which enables the reactions that turn neutrons into protons, and vice versa. The researchers showed that tweaking the other three fundamental forces could compensate for the missing weak nuclear force and still allow stable elements to be formed.

That study and the MIT work are different from most other studies in this area in that they examined more than one constant. “Usually people vary one constant and look at the results, which is different than if you vary multiple constants,” says Mark Wise, professor of physics at Caltech, who was not involved in the research. Varying only one constant usually produces an inhospitable universe, which can lead to the erroneous conclusion that any other congenial universes are impossible.

One physical parameter that does appear to be extremely finely tuned is the cosmological constant — a measure of the pressure exerted by empty space, which causes the universe to expand or contract. When the constant is positive, space expands, when negative, the universe collapses on itself. In our universe, the cosmological constant is positive but very small — any larger value would cause the universe to expand too rapidly for galaxies to form. However, Wise and his colleagues have shown that it is theoretically possible that changes in primordial cosmological density perturbations could compensate at least for small changes to the value of the cosmological constant.

In the end, there is no way to know for sure what other universes are out there, or what life they may hold. But that will likely not stop physicists from exploring the possibilities, and in the process learning more about our own universe.

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User comments : 37

"A definitive answer is impossible"; String Theory is untestable, so we will never know if it is the truth; and...under "comments that will be deleted" -- "pseudoscience theories".

Think back to the beginning -- if a down quark happened which was lighter than the up quark, and protons up to a percent heavier than neutrons were created etc., etc., but they can't exist, and in what reality could they??? One which cannot be tested, let alone realized!

There is only one Universe, the one in which the logical assemblage of particles that can exist do exist. Laws are intangible, rules follow laws, so any other Universe is pure fantasy. Why can't these guys get into researching something constructive and useful?

@baudrunner: This article was mostly looking at the ramifications of different physical constants. The quark masses were only part of it. With different pysical constants (including particle masses) rules can still follow laws. It's a thought exercise. You never know where they'll lead. Without Einstein's thought exercises it might have taken us another 10 years to duplicate the ideas in his three major papers.

exactly -- thought exercises are where most of our major fringe theories lie now anyway. String theory based on which ever m-brane or s-brane mathematics is all a thought experiment -- for that matter like stated previously Eisntien Bohr debates were thought experiments.

Most people taking on this one try to theorize is carbon would be stable in these alternate universes and if so then life could probably exist as we know it today... the as we know it caveat is important, because until we can prove that life based on a different energy release mechanism exists then we must assume only life as we know it exists... unfortunately.

Are heaven, hell and purgatory considered alternate universes with different rules and physics? Funny how most physicists, and other supposedly intelligent and open-minded individuals eagerly entertain utterly unprovable speculations about things such as multiple universes, p-branes, black branes, D-branes etc.,through nothing other than faith alone yet absolutely reject the possibility of God and scoff at those with religious faith. Were we not told almost 2,000 years ago that "In my Father's house are many mansions"? This sounds like multiple universes to me. And this was long before string theory came into being.

That should roughly be the direction of how it goes, not the other way around. This is not an Egg/Chicken problematic.

Altering the masses (and essentialy the ratio between them aswell) and calculating to see "how it fares" under given conditions is nothing more than a thought exercise. The masses of protons, neutrons, etc. and the ratios between them are all results of self-assembly based on the equilibrial states at a certain scale.

Well, atleast there is a chance that the scientists involved get smarter from all the brain-exercising ;-)

No, heaven, hell and purgatory are not alternate universes. Travel between universes is impossible -according to the same theory that makes them sensible. Since you go to one of the above three when you die (according some immature branches of the christian mythology) they are not alternate universes. They may be largely isolated regions of this universe, however, if they existed.

And scientists don't believe in these things because of "faith" but because they are the logical or mathematical consequences of the theories which have demonstrated their reliability countless times and have not yet been disproved. I suppose you'd prefer they try to predict the weather or design a building by interpreting the entrails of a slain goat?

Fascinating research! I have always wondered what would happen if some of basic constants would change, and most importantly, how far can you push these changes and still get something sensible and complex. With simulations like these, we could finally understand not only how large the constants are, but why are they as they are and what would happen if they werent...

Wrong conclusion. String theory is _at this moment_ untestable.Wrong scientific thinking: There is no "truth" in science, there are instead models which are not (yet) falsified. "Truth" is a matter of philosophy, not of science.

It's a thought exercise. You never know where they'll lead.

This is a passe-partout. It's good for everything (inclusively reasoning about angels and demons) and thus good for nothing.Speculating about multiverses will never be of any scientific use.

String theory based on which ever m-brane or s-brane mathematics is all a thought experiment

Wrong. String theory is not an invention, it is an ongoing discovery. A discovery with the option to answer some of the deepest questions of physics. An option that - by principle - no multiverse speculation has to offer.

No, heaven, hell and purgatory are not alternate universes. Travel between universes is impossible -according to the same theory that makes them sensible. Since you go to one of the above three when you die (according some immature branches of the christian mythology) they are not alternate universes. They may be largely isolated regions of this universe, however, if they existed.

And scientists don't believe in these things because of "faith" but because they are the logical or mathematical consequences of the theories which have demonstrated their reliability countless times and have not yet been disproved. I suppose you'd prefer they try to predict the weather or design a building by interpreting the entrails of a slain goat?

Wow. An expert in theology as well as string theory. I should be in awe. So on what do you base your knowledge that "travel between universes is impossible". On proof from immature branches of physics, which cannot be tested?

So on what do you base your knowledge that "travel between universes is impossible".

It's the definition of "universe". What's your definition?

Semantics arguments are the most head-splitting kind.

I think what frajo is saying is that its considered a different universe, because when youre in it, its all there is. It is the very fabric of reality that you occupy, all things included in however many spacial or time, or whatever kind of dimensions there are to it.But I can also see the other argument that would state that if there is a multiverse, and even if each "universe" were a closed system with it's own dimensionality,Wouldnt we just call the multiverse the universe? The answer is yes, but we could never know if there is a multiverse, so its a moot point.

What we can do though is test for other dimensions within our universe that may be superimposed on our own, and fijo, I wouldnt be so hard on Gammakozy for believing that these demensions might be occupied.

Are heaven, hell and purgatory considered alternate universes with different rules and physics? Funny how most physicists, and other supposedly intelligent and open-minded individuals eagerly entertain utterly unprovable speculations about things such as multiple universes, p-branes, black branes, D-branes etc.,through nothing other than faith alone yet absolutely reject the possibility of God and scoff at those with religious faith. Were we not told almost 2,000 years ago that "In my Father's house are many mansions"? This sounds like multiple universes to me. And this was long before string theory came into being.

Most scientists don't scoff at the idea or possibility of God. God if he exists is entirely outside the realm of science, so the issue is simply irrelevant.

Nothing new. But theorizing without at least principally falsifiability is an antagonism. It's speculating, not theorizing.

So its speculating. What of it? Many speculations once considered untestable were proven so given enough time and advances in technology. Multi-universe theories may not be a testable hypothesis today, but that doesn't means we can never discover echoes of their formation in this one.

.."The observed values of the dimensionless physical constants (such as the fine-structure constant)... are balanced as if fine-tuned to permit the formation of commonly found matter and subsequently the emergence of life. A slight increase in the strong nuclear force would bind the dineutron and the diproton, and nuclear fusion would have converted all hydrogen in the early universe to helium. Water and the long-lived stable stars essential for the emergence of life would not exist. Small changes in the relative strengths of the four fundamental interactions can greatly affect the universe's age, structure, and capacity for life"..

The ekpyrotic scenario harkens back to conditions before the Big Bang, for one.

The ekpyrotic scenario is very elegant, as it integrates the mainstream concept of a BigBang while dissolving its mainstream problems like the idea of a beginning of time.But as the ekpyrotic "BigBang" is only a special (repeating) event happening to colliding branes in a higher-dimensional world there is no notion of multiple universes. "Our" brane is not a universe separated from other universes but all branes are components of one common universe. Whether we'll ever be able to get information from other branes remains an open question but it can't be ruled out.

Somewhat OT, but I came across this paper "Bacterial survival in Martian conditions" posted by a group of Italian researchers who are attempting to expose Earth life to the rigors of Mars, with little success. The paper's at: http://arxiv.org/...77v1.pdf FWIW.

"Our" brane is not a universe separated from other universes but all branes are components of one common universe.

From where you got such idea? Anyway, its relevance just depends on the parallel universe definition. If it's scale invariant, then the galaxies are tiny universes formed at the nodes of dark matter foam as a products of their collisions, but whole system can be encapsulated into black hole, formed in the same way at larger scale recursively, because there is no apparent lower or upper limit in brane size.

But my point is, you cannot observe/interact with remote or parallel universe, until it's not based one similar physical principles - and after then the life similar to terrestrial one could evolve in it too. Therefore just the observability is the criterion of anthropocentric principle here.

In my opinion Universe is completely random stuff and it's appearance just follows from observability/visibility of randomness, i.e. laws of transversal energy spreading through random dense gas. There is no apparent evidence of lower or upper limit of this simulation, because Universe appears as random at sufficiently general level, as the randomness could be.

These vortices can be visualized by Lorentz microscopy in thin layers of superconductor, so we can observe the flow of vortices, their mutual annihilation and so on... And because they repel mutually and they're elastic, they could form a waves too...

Considering the diversity of human life here on Earth, I can't consider possibility of life in other Universes a very attractive one at all. Life on other planets around stars relatively near to ours will be weird enough. Their relationship with time is so diferent from ours, because ours is based on our proximity to sun; effect of sun's gravitational pull and gravitational pull on us by earth; speed of rotation and orbit around sun; speed of sun's path around galactic center; distance from galactic center; mass and nature of star -- blue? yellow? red? and so on.

by ekpyrotic model universe was formed by brane collision, after then these branes cannot be components of this universe.

whether your opinion is based on a physical theory

my theory is necessary result of Occam's razor criterion: i.e. the attempt for removal all necessary postulates. Our Universe isn't empty, so that infinite random stuff is the second most simple option.

There is only one Universe, the one in which the logical assemblage of particles that can exist do exist. Laws are intangible, rules follow laws, so any other Universe is pure fantasy. Why can't these guys get into researching something constructive and useful?

I fully agree. Even if there were multiple universes, how are they separated? How can 1 be completely independent of the rest? How can a Big Bang of one Universe not effect the rest? Why would we assume any other Universe would have any different properties than our own? In fact, I think we could well assume that a different Universe would have the same properties as our own because we know our Universe exists with these properties. We have no evidence other Universes exist with different properties so there is not as much of a reason to believe they would be different.

In the time of Galileo he proposed that we were not the center of the universe, but we do believe that we are the only thing that has existed and will exist. We want to believe that time and matter begins and ends with this universe. If the number of universes are infinite and the sum of space is infinite, would that, also, make time infinite? If you went back 13 trillion years ago, what would we see? If matter can neither be created nor destroyed, would that, also, prove that matter evolves up and down the periodic table infinitely? What would we see if we, instead of looking to the center, looked down or up to see what is above or below us; would we see another universe(s)that might be a million times larger that our own? Why is our universe expanding? Could we be a dwarf universe?